I ran mine in one tube (#4 & #8) close to the heads for a couple of years. Then I moved them to the collector about 40" from the heads. Worked both ways. I had other issues when I had them close to the heads, so I don't know if the O2 location did not work as well as it should have. Now I make 402 rear wheel horsepower, 416 tq with a 302 stroked to 354. Runs great. Cruise at 1300 to 1500 rpms in 5th gear. No issues, but the rear tires will not stick to the road
Dwight
I'm using the EECIV Ford unit with a custom chip.